Modelamento biomecânico da atuação de aparelhos com parafuso expansor sobre estruturas mandibulares assimétricas através do método de elementos finitos

Abstract

Occlusion disorders, resulting from changes in the development of the arches are commonly found in the population. Lead to dysfunctions and changes in mastication, speech and breathing. Usual techniques for treating these disorders require the use of orthodontic/orthopedic apparatus that use expansion screws. The gradual displacementimposed by their activation leads to bone remodeling and a new equilibrium position of the arches. It is necessary to use a methodology that relates the displacement caused by the screw with the deformation in the bone structure, quantifying the strength levels achieved and the stress distribution in the buccal structures. This work aims to develop abiomechanical model of the acting of expansion screw appliance on asymmetric mandibular structures by finite element method. A biomechanical model of the complete jaw-mucosa-expander was built using CT images of the human jaw and computer software for the construction of geometric solids. An iterative procedure was developed to deal with a boundary condition that takes into account the mandibular asymmetries. The results obtained by simulation showed asymmetries in the distribution of contact pressures and indicated with precision the diagnosis of the patient's malocclusion. It was shown that theleft and right ends of the expansion screws move differently in relation to the mandible studied. The contact pressure between the apparatus and the mucosa varied linearly with the applied force. A bench was developed to measure in vivo contact pressures using piezoelectric sensors. The in vivo measurements agreed with the computational results, validating the model. The biomechanical modeling proposed in this work proved to be a useful tool to control and optimize malocclusion treatments, safely avoiding the use of forces acting in live structures beyond the biological tolerance, which could result in traumatic effects.